1. Heat the oil in a large, non-stick skillet (preferably one with a lid) over med-high heat. Add onions and saute until tender and beginning to brown, about 10 min.

2. Stir in the red peppers and cook 10 more min., stirring often. Mix in the sugar, vinegar, salt, and pepper. Reduce heat to med., cover the pan, and cook until the mixture is very soft and the juices are somewhat caramelized, about 20 more min. Stir occasionally.